在Neo4J中，如何在Java的cypher查询中将标签设置为参数？ [英] In Neo4J, how to set the label as a parameter in a cypher query from Java?
问题描述
我在Java中使用Neo4J中的cypher参数时遇到问题。我运行嵌入的数据库。
I have problems with parameter in cypher in Neo4J from Java. I run the the database embedded.
代码应该是这样的（GraphDB.cypher直接转到ExecutionEngine）
The code should be like this (GraphDB.cypher goes directly to the ExecutionEngine)
HashMap<String, Object> parameter = new HashMap<>();
parameter.put("theLabel1", "Group");
parameter.put("theRelation", "isMemberOf");
parameter.put("theLabel2", "Person");
GraphDB.cypher("MATCH (n1:{theLabel1})-[r:{theRelation}]->(n2:{theLabel2}) RETURN n1, r, n2", parameter);
但它以此例外结束
Exception in thread "main" Invalid input '{': expected whitespace or a label name (line 1, column 11)
"MATCH (n1:{theLabel1})-[r:{theRelation}]->(n2:{theLabel2}) RETURN n1, r, n2"
文档（和教程）告诉使用{}来覆盖参数，但这也用作属性的cypher json表示法。
@参见 http://docs.neo4j.org /chunked/milestone/tutorials-cypher-parameters-java.html
The documentation (and tutorial) tells to use the { } to cover the parameters, BUT this is also used as the cypher json notation for properties. @See http://docs.neo4j.org/chunked/milestone/tutorials-cypher-parameters-java.html
是否有其他方法可以解决此问题，而不是像这样构建查询字符串（或者使用其他模板方法）
Is there another way to solve this issue rather than building the query string like this (or with other template methods)
GraphDB.cypher("MATCH (n:" + labelName + ")-[r:" + relationName + "]->...
这是必需的，因为目标标签可以更改我想完全重复使用代码。
This is needed because the target label can change and I want to reuse the code completly.
提前致谢。
[[获得后获得的信息] A（叹气）没有作为答案]]
由于这种形式的参数目前（2014.6）不受支持，我会在发送之前运行一点替换器查询。
Since this form of parameter is currently (2014.6) not supported, I will run a little replacer right before sending the query.
HashMap<String, Object> parameter = new HashMap<>();
parameter.put("theLabel1", "Group");
parameter.put("theRelation", "isMemberOf");
parameter.put("theLabel2", "Person");
parameter.put("aName", "Donald Duck");
GraphDB.cypher("MATCH (n1:#theLabel1#)-[r:#theRelation#]->(n2:#theLabel2#) WHERE n2.Name = {aName} RETURN n1, r, n2", parameter);
... with ...
public static ExecutionResult cypher(String query, Map<String, Object> params) {
for (String key : params.keySet()) {
query = query.replaceAll("#" + key + "#", String.valueOf(params.get(key)));
}
return params == null ? cypherEngine.execute(query) : cypherEngine.execute(query, params);
}
可以有更多的可读
推荐答案
我担心目前不支持这种情况。
I am afraid this is not supported at the moment.
这可能与原因完全相同本期中解释的一个： https://github.com/neo4j/neo4j/pull/1542 。
And it might for the very same reason than the one explained in this issue: https://github.com/neo4j/neo4j/pull/1542.
参数化查询背后的想法是重用（缓存）执行计划。如果节点标签或关系类型不同，则执行计划根本不会相同，从而破坏了执行计划缓存的有用性。
The idea behind parametrized queries is to re-use (cache) execution plans. If a node label or a relationship type varies, the execution plan wouldn't be the same at all, thus ruining the usefulness of execution plan caching.
这篇关于在Neo4J中，如何在Java的cypher查询中将标签设置为参数？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
